Variable focus objective

ABSTRACT

A variable-focus objective comprises in order starting from the front, a first divergent fixed-focusing group, two movable groups, one convergent and the other divergent, said two movable groups filling the role of variator and compensator at the same time, and a fixed convergent rear group, said first group comprising at least three lenses of which the first is a convergent lens, the others being divergent, and of the following limiting ratios for the radii of curvature: WHERE F1 IS THE FOCAL DISTANCE OF THE FOCUSING GROUP. The first fixed group may include 3 or 4 lenses of which one is convergent and the others divergent. The focusing distance is 2f1 to 3f1 and the zoom ratio is about 5.

United States Patent [72] Inventors Row-Fat Lal:

Christian Lletar, both of Yverdon Vand, Switzerland [2|] Appl. No. 857,814 [22] Filed Sept. l5,l969 [45] Patented Sept. 7, 19'" [7 3] Assignee Palllard S.A.

Vaud, Switzerland [32] Priority Oct. l0, I968 [33] Switzerland [3 1) 15136168 (54] VARIABLE FOCUS OBJECTIVE 6 China, 6 Drawlng Figs. [52] 350/186, 350/220 [5 l Int. Cl G02b 1 5[ l 6 00% 9/34 [50] I'leldotSear-eh 350/184, 186, 220

[56] References Cited UNITED STATES PATENTS 3,152,211 10/1964 Cox et al 350/l84 Primary ExaminerDavid Schonberg Assistant Examiner-Paul A. Sacher Attorneys-Emory L. Grofi' and Emory L. Grofl', Jr.

ABSTRACT: A variable-focus objective comprises in order starting from the front, a first divergent fixed-focusing group, two movable groups, one convergent and the other divergent, said two movable groups filling the role of variator and compensator at the same time, and a fixed convergent rear group, said first group comprising at least three lenses of which the first is a convergent lens, the others being divergent, and of the following limiting ratios for the radii of curvature:

1 1 1 l fl l hl 5 I S I 6I where f, is the focal distance of the focusing group. The first fixed group may include 3 or 4 lenses of which one is convergent and the others divergent. The focusing distance is 2f, to 3f, and the mom ratio is about 5.

PATENTEUSEP Han 3.603.669

sum 1 or 2 INVENT OR Kmu- FAT 14 BY aaz/ ATTORNEY V ARIABLE FOCUS OBJECTIVE The present invention relates to a variable-focus objective comprising, in order starting from the front, a first divergent fixed-focussing group, two movable groups, one convergent the other divergent, these two movable groups filling the functions of variator and compensator at the same time, and a convergent fixed rear group.

In objectives of this type, the shortest distance of focusing, mltoned between the object and the front lens, is in general rather large, of the order of l6 to 201], I, being the absolute value of the focal distance of the focusing group.

It is an object of the invention to enable the achievement of much shorter focusing distances, of the order of 2 f, to 3 f, without this spoiling the quality of the objective which can be very well corrected.

According to the invention, there is provided a variablefocus objective comprising, in order starting from the front, a first divergent fixed-focusing group, two movable groups, one convergent and the other divergent, these two movable groups filling the functions of variator and compensator at the same time, and a convergent fixed rear group. This objective is characterized in that the first group comprises at least three lenses of which the first is a convergent lens, the others being divergent, and by the following limiting ratios for the radii of curvature:

where f, is the focal distance of the focusing group.

In order that the invention may be more fully understood one embodiment and one variation of the objective according to the invention, are described below, purely by way of illustrative but nonlimiting examples, with reference to the accompanying schematic drawing in which:

FIG. I is a schematic section of the said embodiment;

FIG. 2 is a section analogous to that of FIG. 1, showing the variation of the said embodiment; and

FIGS. 3 to 6 illustrate the corrections of the aberrations of the objective shown in FIG. 1.

With reference to FIG. I, the objective comprises a first group [of four lenses L to L, of which the axial position may be modified to ensure focusing adjustment. The total power of this group is negative, so that this goup constitutes a divergent system.

The objective also comprises three other groups, of which two groups II and III are movable to ensure focal variation and stability of focal length whilst group IV is fixed.

Group II includes four lenses L to L and constitutes a convergent system, whilst group III comprises three lenses L, to L, and constitutes a divergent system.

Group IV includes six lenses L to L and constitutes a convergent system. The second lens L, of this group is an optical flat, this flat comprising a semireflecting surface S intended to send back a portion of the light beam towards a viewing device which is not shown in the drawing. However, this flat has been considered in the following as being a lens of which the two faces have an infinite radius of curvature.

According to one embodiment, the objective shown can have the characteristics indicated in the following table. In this table, the radii of curvature are numbered starting from the first surface of the front lens, but they have not been indicated in the drawing in order not to overcrowd the latter. These radii are positive when the center of curvature occurs on the side of the focal plane F with respect to the apex of the surface under consideration, and negative when the center of curvature is on the object side. The value of the radii is indicated by a multiplication factor of the absolute value of the focal distance f, from the focusing group I. This is the same for the lens thicknesses designated by d and for the spaces between the lenses designated by a. The refractive index of the glass of each lens is indicated under n, whilst the constringence, or Abbe number, is indicated under v.

L R 4! 7| I lit-8.510 L1 I O-IM 1. 80518 i 35. I

31- -8-510 R. a iii-0.0010 I4 lit-0.0900 I. 02011 60. I

RIILII 01-01)) Rs 4.509 Ls Iii-0.0860 1. ml M. ll

RU Z.

o-0M0 BI- 2.Id7 Lt dt-o-flm 1. ml U. I

lit-2.2

tls-ll.5972+0.10m Ila-mm L; til-0.1010 1. saw 00. a

Rnl..ml R n m M G-m tl- Ls liq-0.0000 l. I! as. I

Bis-0.8686 a ossss isln. Iii-0.1m 1.6% 60-83 Rn- L620 M G-M0 Bis-0.6698 L ds- 0-1159 1. M1 on. a

Ric-2.681

GIO-W'f'O-"Sl Ru- 2.18ll t (is-0.0200 1. ml 60. a

Bi -0.4173 R o a l-(L840 ts- Ln lim thm 1. mu m- BI ltn omso a 0 mo it I L11 dn=0.0340 1.80518 26.

RB I6.90 R 1 m M =035B1+ILM Q- Ln dn=0M0 I. saw 80. ll

Rul-G.l)

ail-0.01m Ba so Ltttilt-0.1m 1. m on.

Rssw R 0 2m au-o' rr- Ln tin-M300 1. "I50 M. 71

Ru- IL3M R 0 m9 lls-0.07m

ts-- I45 d s-0.0m 18 25.

Btu-03195 R. osm

14s div-0.0600 1. ml 80. I

Rss- 0.281li Ba 0 saw l1------- swam 1. ml 60. 38

RIP 8.l79

tin-0.2884

The resulting focal length of the objective above may vary between 0.l6-[f,| and 0.771], I, which gives a mom ratio of about 5.

The aberration curves of the objective above are given by FIGS. 3 to 6. FIGS. 3 and 4 show for the shortest focus and respectively for the longest focus, the spherical aberrations which are indicated in continuous line and the deviation from the condition of the sines in discontinuous line. FIGS. 5 and 6 show also for the shortest, and the longest focal distance respectively, the tangential curvature indicated in continuous line and the sagital curvature in discontinuous line.

In the variation shown in FIG. 2, the groups II, III, and IV are similar to the corresponding groups of the embodiment of FIG. I. On the other hand, the group I only comprises three lenses L L, L, constituting a divergent system.

In a specific example, these three lenses may correspond to the following data:

wherein R,-R inclusive, are the values of the radii of the refracting surfaces of the component lenses L,-L,, counting I from the front to the rear of said objective lens; 4 d,, inclu- Ll 111-2.? iii-Mom 1 80m 25 a sive, are the values for the axial thicknesses of the lens ele- R'4--4.000 I 5 ments and a e, are the values for the axial distances of the mp8. air gaps between the component lenses and a is the value for L: D 05-00400 1. 02041 00.38 the axial distance of the air gap between the component lens 3 fl-Mm and the focal plane; and counting from the front to the rear of said objective lens, said values for the refractive index and Ru-um l0 Abbe number being those of the respective lens material of sand lenses of sald objective lens.

It will be parent that various chan es and modifications may be he embodimen dcscfiged Win10." dc s 2. An ob ective accordlng to claim I having a zoom ratio of from the essential concept of the invention as defined in scope l about b theappended claims.

claim. 3. An ob ective according to chum 1, wherein the focusing l. A vanab' le focus objective lens comprising, in order startdistance of the order of m ing from the front a first divergent fixed-focusin u of lenses, said group ihcluding at least three lenses th e 2:1 lens A vanable focus comm-8mg "3 of a map being convergent and he othcr'lenses of the mg from the front; a first divergent fixed-focusing group of group being divergent said first lens having a re meniscus lenses, said group including at least three lenses, the first lens spaced from the forward meniscus of the next adjacent lens of of sad T .bems convfrsem and the .other lenses the said group; two movable groups, one convergent and the other group hams dwemcm 6" [cm havmg a '9 mcnmus divcrscm said movable groups fining the re" of variator spaced from the forward meniscus of the next ad acent lens of and compensator at the same time; a fixed convergent rear :P group; Y: movable i r ffi g s 9 fivclens havin the follow. um d 1vergent,sa1 two mova e groups 1 mgt e roeo vanator 8 s e data and compensator at the same time; a fixed convergent rear Re!mc Abba group; said objective lens having the following numerical data: Lens Curvature radius Axial distance ve number index (v) Iii-8.510 Retme- Abbe L1 d1 -0.1000 1. 80018 26. 4B tive number R|= 3-l51 a o 0040 Lens Curvature radius Axial dlstanoo lndsx (v) 1 R1=4.74a R'1=2.007 L1 d1=0.0900 1.611041 60.83 d'1=0.1000 1. 80515 25. 4s

R|=Ll4l R'|= -4.090 R 2 599 01:00am R a 996 11'1=0.(D40

14 44-00000 1.02041 00.1111 1/, lea-0.0400 1. 02041 00.03

34-2009 R4-0.7077 R: m7 us=0.%l0 R 1 1 G's-0.1869 L1 R 22 10-00000 1.02041 0000 40 'L'. 00-00000 1. 02041 00.00

-2.8 5 R. a m a4=0.5972-0.1020 R m2 m-0.5912-0.1020

=5. LI 0 =0.1040 1. 62041 00. as d.=0.1040 1. 02041 00. as

Bis-1.231 u 0 m R;.;- -1.2s1 a 0 m i 1 a 1111-14-85! IMF-14.364 L1 d4=0.0300 1. 80618 20. 43 d.=0.0300 1. 80518 25. 40

311-03080 m 0m R1s=0.8iBB6 a Down RII'O-BBSG R1l=0-m o D In d1=0.1439 1. 62041 60. 33 L1 d1=0.1489 1. 62011 60. 83

R14- -1.020 00M0 R14= --1.620 R11=0.6893 R11=0.6698 7:00am L1 d;=0.11s0 1. 02041 60. 33 L, d4=0.11s9 1. 02041 60.88

Rte-2.631 R1s=2.631 R 2 136 fl =0.0m-0.7781 R 2 135 Gg=0-0302-0-7781 IT= 4 L. a.=o.o2so 1. 02011 00. as 1., a.=0.o200 1. 02041 00. as

R11=0.417s to m R11=0.417s a w B1s= -o.a1s4 R1ll=0.m I L R om du|=0.m 1. 02041 00. 33 L4 R o 5230 d11=0.0m0 1. 02041 00 as sn- R 05200 mao'm R 05m fl 2!" L11 R u go d11=0.0340 1. 80518 26. 43 L" R d11=0.0340 1. 80618 25- 43 a=- 22=-16.90 B 1 m un=0.258l0.0064 R 1 m0 fl11=0.25810.m64

8 ll L14.-." R 1 mo d|,=0.s40 1. 02041 00.33 L,, R 1000 d11=0.340 1. 02041 00. as

R u=o.o100 a11=00100 3: as as a R du=0.l.799 1. 02041 00.33 L 1111:0179!) 1. 02041 00011 g: m a: m

1111=0.0so0 a1|=0.0000 Rn=0.2275 Rr1=0.2275 td-u d1|=0.0o00 1. 69150 54- 71 L d1=0.0600 1- w w 54- 71 Ba- 14as4 R -14.a54 R o m 14=0.07m R 0 3239 a11=0.0700

L14- a1.=o.0200 1.00510 2043 1 0.1=0.02o0 1.80618 2040 Has-0.2196 Rso=D-2l95 R om 0 ,:(10930 R o 8460 61=1D-0980 II I L11 du=00000 1. 02041 00. as L11 I 0= w M2041 60-33 Ru= -02! Rss= 0.2315 R1: 02027 Fawn R 02827 I41 0n=00500 1. 02401 00.33 75 L11 11= 1-6204! 33 Ru= 3.179 R|4= 3.179

tl11=0.m G17=O.289l

and counting from the front to the rear of said objective lens. said values for the refractive index and Abbe number being those of the respective lens material of said lenses of said objective lens. I

5. An ObjQCllVC accordlng to clalm 4. whereln the focuslng distance is of the order of 2], to 3f,.

6. An objective according to claim 4, having a zoom ratio of about 5. 

1. A variable focus objective lens comprising, in order starting from the front; a first divergent fixed-focusing group of lenses, said group including at least three lenses, the first lens of said group being convergent and the other lenses of the group being divergent, said first lens having a rear meniscus spaced from the forward meniscus of the next adjacent lens of said group; two movable groups, one convergent and the other divergent, said two movable groups filling the roll of variator and compensator at the same time; a fixed convergent rear group; said objective lens having the following numerical data:
 2. An objective according to claim 1 having a zoom ratio of about
 5. 3. An objective according to claim 1, wherein the focusing distance is of the order of 2f1 to 3f1.
 4. A variable focus objective lens comprising, in order starting from the front; a first divergent fixed-focusing group of lenses, said group including at least three lenses, the first lens of said group being convergent and the other lenses of the group being divergent, said first lens having a rear meniscus spaced from the forward meniscus of the next adjacent lens of said group; two movable groups, one convergent and the other divergent, said two movable groups filling the role of variator and compensator at the same time; a fixed convergent rear group; said objective lens having the following numerical data:
 5. An objective according to claim 4, wherein the focusing distance is of the order of 2f1 to 3f1.
 6. An objective according to claim 4, having a zoom ratio of about
 5. 